<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* css */
        .demo1-bg1 {
            width: 100px;
            height: 100px;
            display: -webkit-box;
            -webkit-box-pack: center;
            -webkit-box-align: center;
            margin: 50px auto;
            background: #fff;
            border-radius: 50%;
            box-shadow: 0 0 0 10px red inset;
        }

        .demo1-bg2-1,
        .demo1-bg2-2 {
            position: relative;
            margin: 0;
            padding: 0;
            -webkit-box-flex: 1;
            height: 80px;
            background: #fff;
            border: 10px solid grey;
        }

        .demo1-bg2-1 {
            border-radius: 50px 0 0 50px;
            border-color: grey transparent grey grey;
            transform-origin: 100% 50%;
            z-index: 1;
        }

        .demo1-bg2-2 {
            border-radius: 0 50px 50px 0;
            border-color: grey grey grey transparent;
            transform-origin: 0 50%;
            z-index: 2;
        }
    </style>
</head>

<body>
    <div class="demo1-bg1">
        <div id="J_bg2_1" class="demo1-bg2-1"></div>
        <div id="J_bg2_2" class="demo1-bg2-2"></div>
    </div>

</body>

</html>